Inside Back Cover: Next Generation of Zinc Bisguanidine Polymerization Catalysts towards Highly Crystalline, Biodegradable Polyesters (Angew. Chem. Int. Ed. 48/2020)

Many bioplastics are produced by metal-catalyzed ring opening polymerization. For a truly sustainable lifecycle the industrially used cytotoxic catalyst tin(II)-2-ethylhexanoate must be replaced by non-toxic alternatives. In their Research Article on page 21778, L. Hartmann, S. Herres-Pawlis, and co-workers report the fastest known robust catalyst for the polymerization of lactide (LA) and ϵ-caprolactone (CL). This zinc guanidine catalyst polymerizes technical LA and CL in the melt with high rate constants and molar masses, giving a colorless, transparent polymer.